linux-kernel - [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject

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Date:   Fri,  3 Sep 2021 03:30:34 +0000
From:   Jiang Jiasheng <jiasheng@...as.ac.cn>
To:     rostedt@...dmis.org, mingo@...hat.com
Cc:     linux-kernel@...r.kernel.org, Jiang Jiasheng <jiasheng@...as.ac.cn>
Subject: [PATCH 2/2] tracing: Add trace_trigger_soft_disabled() in front of trace_event_buffer_reserve() in trace_inject_entry()

Directly use trace_event_buffer_reserve() might be unsafe,
as we can see from the trace_trigger_soft_disabled() of
'include/linux/trace_events.h' that if the value of
file->flags is 256, the check in the trace_trigger_soft_disabled()
will be passed but actually shouldn't have.
Therefore, we suggest that trace_trigger_soft_disabled()
should be added in front of the trace_event_buffer_reserve()
in trace_inject_entry().

Signed-off-by: Jiang Jiasheng <jiasheng@...as.ac.cn>
---
 kernel/trace/trace_events_inject.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_events_inject.c b/kernel/trace/trace_events_inject.c
index c188045..6dfd3cd 100644
--- a/kernel/trace/trace_events_inject.c
+++ b/kernel/trace/trace_events_inject.c
@@ -21,6 +21,8 @@ trace_inject_entry(struct trace_event_file *file, void *rec, int len)
 	void *entry;

 	rcu_read_lock_sched();
+	if (trace_trigger_soft_disabled(file))
+		return written;
 	entry = trace_event_buffer_reserve(&fbuffer, file, len);
 	if (entry) {
 		memcpy(entry, rec, len);
-- 
2.7.4